Fix decoding unicode values in the config object passed to the browser

[bahmutov]

• Closes Cypress.env() return value is garbled when multibyte string in 3.5.0 #5435
• related to base64 encode the embedded runner config object so it can't b… #5155
• failing demo in 3.5.0 passes with this fix add failing v3.5.0 env test with unicode value cypress-example-recipes#353

User-facing changes

Environment variables with unicode values are correctly passed to the runner again. In 3.5.0 we have accidentally broken them by encoding resolved Cypress config object incorrectly. This became a problem for anyone using Unicode characters in their environment variables in the configuration file like

{
  "env": {
     "greeting": "привет"
  }
}

PR Tasks

• Have tests been added/updated?

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Internal

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[jennifer-shehane]

I confirmed that this fixes the original issues bug with the あいうえお characters.

I didn't review the code specifically.

[flotwig]

Wow, didn't know that atob didn't work with Unicode. Nice fix, LGTM